High voltage coaxial connector



Oct. 6,1970

H. B. MCFARLANE ,3,533,047

HIGH VOLTAGE COAXIAL CONNECTOR Filed April l1, 1969 INVENTOR.

HUGH B. MCFARLANE TTORNE Y 3,533,047 HIGH VOLTAGE COAXIAL CONNECTOR HughB. McFarlane, Livermore, Calif., assignor to the United States ofAmerica as represented by the United States Atomic Energy CommissionFiled Apr. 11, 1969, Ser. No. 815,372 Int. Cl. H01r 17/18, 7/02 ILS. Cl.339-94 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTIONThe instant invention was evolved in the course of, or under, ContractW-7405-ENG-48 with the United States Atomic Energy Commission.

Conventional coaxial cable includes an inner conductor, an insulatingsleeve of polyethylene, or the like, coaxially disposed about the innerconductor and bonded thereto, a woven outer or shielding conductorformed concentrically about the insulating sleeve, and an outer jacketof insulating material about the shielding conductor. Connection of suchcable to various electrical equipment is commonly accompanied by meansof a quick coupling-decoupling coaxial jack connector in order that thecable may be readily connected to, or disconnected from the equipment asdesired. A coaxial connector of this type generally includes a plug, orequivalent terminal element, electrically connected to the innerconductor of the cable, and a cap, or equivalent terminal element,electrically connected to the shielding conductor of the cable. The capis coaxially disposed upon a coaxially extended portion of theinsulating sleeve of the cable from which the insulating jacket andshielding conductor have been removed, such extended portion of thesleeve encompassing the end portion of the inner conductor to which theplug is connected. To facilitate electrical connection of the connectorterminal elements associated with the cable, to the electricalequipment, the connector typically further includes an insulating bodysecured to a conductive panel of the equipment, the body having acylindrical bore in coextensive registration with an aperture throughthe panel and being provided with a terminal jack at the end of the borein spaced relation to the panel. The extended portion of the cablesleeve is removably insertable into the bore to removably engage theplug in the terminal jack and thus electrically connect the cable innerconductor thereto. When the plug is thus engaged in the jack, the cap orother terminal element connected to the shielding conductor of the cableis engagable with a complementary terminal element conductivelyassociated with the panel, such as a conductive annular boss projectingfrom the panel in circumscribing relation to the aperture therethrough.In this manner, the shielding conductor is electrically connected to thepanel terminal element.

With a conventional coaxial connector of the type described above, it isto be noted that an air space inherently exists between the coupledinner terminal elements, Le., plug and jack, and coupled outer terminalelements, i.e.,

cap and boss. lIn this regard, the air space is defined by r tred StatesPatent O 3,533,047 Patented Oct. 6, 1970 ice the annulus between theextended portion of the insulating sleeve of the cable and the bore wallof the insulating body. Thus, the voltage standoff capability of theconnector between the coupled inner and outer terminal elements islimited to that of the ionization potential of air. More particularly,if the applied potential between the inner and outer terminal elementsexceeds the ionization potential of air, charged particles may beuninhibitedly accelerated the entire length of the air space, causingionization velocities to be reached and thus ionization breakdownbetween the terminal elements. As a result, the voltage stand-olicapability of such existing connectors is typically limited to fromabout 20 to 50 kilovolts.

In order to increase the voltage stand-off capabilities of existingcoaxial connectors of the foregoing type, it has been the usual practiceto iill the air space separating the inner and outer terminal elementsthereof with a medium having good dielectric properties. For example,the air space is typically potted with a solid dielectric material, orfilled with an insulating dielectric liquid. Another conventionalpractice involves pressurizing the air space with a gas having gooddielectric properties. However, it will be appreciated that the quickcoupling-decoupling feature of the connector is nulliiied by any of theforegoing measures to increase the voltage stand-off capability thereof.

SUMMARY OF THE INVENTION The general object of the present invention isto provide a coaxial jack connector having a quick couplingdecouplingaction in conjunction with an outstanding high voltage stand-offcapability.

The connector of the invention is generally of the type describedhereinbefore wherein coaxially spaced coupled inner and outer terminalelements are separated by an inherently existing intervening annular airspace delined between an extended insulating sleeve portion of a coaxialcable and the bore wall of an insulating connector body. However, inaccordance with the particularly salient aspects of the invention, theair space is compartmentalized into sealed chambers by a plurality ofcoaxially spaced O-rings, or equivalent hermetic seals which permit asliding t between the cable sleeve and bore wall of the connector body.The seals thus do not interfere with the quick coupling-decouplingaction of the connector. Yet, by virtue of the sealed chambers therebyprovided, acceleration of charged particles the entire length of the airspace between the coupled inner and outer terminal elements iseffectively impeded. The probability of particles being accelerated toionization velocities productive of ionization breakdown is materiallyreduced and hence the voltage stand-off capability of the connectorgreatly increased.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing is across-sectional view taken at a diametric plane through a preferredembodiment of a coaxial connector .in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawing in detail, there is shown a quick coupling-decoupling highvoltage coaxial connector, in accordance with the present invention, forfacilitating connection of a coaxial cable 11, or the like, toelectrical equipment which includes a panel 12 of electricallyconductive material. The cable is provided with an inner conductor 13,an insulating sleeve 14 of polyethylene, or the like, coaxially disposedabout the inner conductor and bonded thereto, a woven outer or shieldingconductor 16 concentrically formed about the insulatsleeve, and an outerjacket 1`7 of appropriate insulating material disposed concentricallyabout the shielding conductor. The shielding conductor and jacket areterminated short of the ends of the sleeve and inner conductor so as toprovide a coaxially extended sleeve portion 18 encompassing the endportion of the inner conductor. Longitudinally spaced quickcoupling-decoupling connector terminal elements are then provided inconnection with the respective ends of the inner conductor and shieldingconductor. In this regard, a banana plug 19 is preferably connected tothe end of the inner conductor to project coaxially from the end of theextended sleeve portion, which is best tapered, as indicated at 20, forpurposes subsequently described. In addition, a conductive cap 21 ispreferably coaxially disposed upon extended sleeve portion 18 andconnected t0 the end of the shielding conductor longitudinally rearwardfrom the plug. More particularly, a conductive sleeve 22 isadvantageously coaxially disposed about the sleeve portion 18 adjacentthe end of the shielding conductor. The cap is rotatably coaxiallymounted upon the sleeve 22 with an outwardly flared annular flange 23thereof abutting the inner face of the end wall of the cap. Theshielding conductor 16 is secured to the sleeve 22, as by soldering,rearwardly, of the cap. In this manner, the sleeve 22 facilitieselectrical connection of the shielding conductor to the cap, whilepermitting cap rotation. The cap is preferably internally threaded, asindicated at 24, for reasons subsequently discussed herein.

The connector further includes terminal elements in association with theelectrical equipment for quick coupling-decoupling connection with theplug 1-9 and cap 21 terminal elements of the cable 11. In general, theelectrical equipment terminal elements are complementary to the cableterminal elements so as to facilitate releasable conductive engagementthereby. More particularly, there is provided an insulating body 26 ofdielectric material, such as a suitable plastic, secured to theconductive panel 12 of the electrical equipment. The body is providedwith an elongated bore 27 normal to the panel and in coextensiveregistration with an aperture 28 therethrough. The bore terminates in acoaxial conductive jack 29, or other terminal element, in spacedrelation to the panel and complementary to the plug 19, or otherterminal element connected to the inner conductor of the cable. The jack29 is best recessed into the insulating body 26 and secured thereto asby means of fasteners, such as screw 31. The jack is provided with a lug32, or is otherwise arranged for convenient connection to the highvoltage circuit portion of the electrical equipment.

Electrical connection of the cap 21, or other terminal element connectedto the outer shielding conductor 16 of cable 11 to the panel 12 of theelectrical equipment is facilitated by a complementary terminal elementin electrical connection therewith, in the illustrated case a conductiveannular boss projecting from the panel in circumscribing relation to theaperture 28 therethrough. The boss may be defined, for example, by aconductive annular nipple member 34 having an outwardly flared flange 36secured to the panel about the aperture thereof `with the bore of themember in coextensive registration with the aperture. Securance of thenipple member to the panel may be accomplished by means of suitablefasteners, such as screw 37 extending through the ange and panel intothreaded engagement with the body 26. Since in the present case the capis internally threaded, the boss is externally threaded to facilitatescrewed connected of the cap thereon.

It will be appreciated that to the extent thus far described, thecoaxial connector is substantially conventional. Quick coupling of thecable 11 to the electrical sleeve portion 18 through the bore of thenipple member 34 and panel aperture 28, into the bore 27 of the body 26to removably engage plug 19 in terminal jack 29. Cap 21 is screwed uponthe nipple member 34 to thereby complete the connection. It isparticularly important to note that an annular air space inherentlyexists between the periphery of the extended sleeve portion 18 and wallof the bore 27. Such air space separates the coupled inner and outerterminal elements, i.e., separates the coupled plug and jack from thecoupled cap and nipple. Typically an applied high voltage exists at thecoupled inner terminal elements while the coupled outer terminalelements are at ground potential. In other words, the inner and outerterminal elements are oppositely polarized, and a potential gradientexists therebetween through the air space. Normally, the potentialgradient would be effective to accelerate charged particles, such asstray electrons, the entire length of the air space. The applied voltagewould consequently be limited since the particles may be unimpededlyaccelerated to ionization velocities. Such accelerated particles wouldundergo ionizing collisions with gas molecules in the air space andcause ionization breakdown between the inner and outer terminalelements. The high voltage stand-off capability of the connector wouldthus be normally limited. Although the stand-off capability may beincreased by filling the air space with high dielectric material, thequick couplingdecoupling feature of the connector is then lost.

In accordance with the particularly salient aspects of the invention,the high voltage stand-off capability of the connector is materiallyincreased while the quick coupling-decoupling feature is retained. Inthis regard, the air space is compartmentalized into a longitudinalsuccession of sealed chambers 38 by a plurality of coaxially spacedresilient O-rings 39, or equivalent hermetic seals which permit asliding iit between the extended sleeve portion 18 and Wall of bore 27.The O-rings are preferably partially recessed into circumferentialgrooves 41 provided in the wall of bore 27, or alternatively intocircumferential grooves provided in the periphery of extended sleeveportion 18. In either case, the O-rings permit slidable insertion of theextended sleeve portion into the bore to facilitate quick couplingengagement of the inner and outer terminal elements, and are slightlycompressed to provide the compartmentalizing hermetic seals in the airspace. The O-rings may be coated with a silicone grease, or the like, tofurther enhance both their sealing action and sliding action. Thetapered end 20 of the extended sleeve portion is of further assistancein facilitating the ready slidable insertion thereof into the bore.

With the air space thus compartmentalized by the O-rings 39 into thesuccession of sealed chambers 38 between the coupled inner and outerterminal elements, it will be appreciated that the probability ofionization breakdown is materially minimized. More particularly, thedistance over which a particle may be accelerated by the potentialbetween the coupled inner and outer terminal elements is now limited tothe length of each chamber 38. Consequently, the velocity to which aparticle may be accelerated is proportionately reduced and the voltagethat may be applied between the inner and outer terminal elementswithout causing ionization velocities to be attained is increased. As aresult the voltage stand-off capability of the connector is materiallyincreased. In actual practice increases in the stand-off capacity of atleast 300% are readily obtainable with connectors in accordance with thepresent invention.

I claim:

1. A coaxial connector comprising a coaxial cable having an innerconductor, an insulating sleeve coaxially disposed about the innerconductor and bonded thereto, an outer conductor concentrically formedabout the sleeve, and an insulating jacket concentrically disposed aboutthe outer conductor, said sleeve including an extended portionencompassing an end portion of said inner conductor and projectingcoaxially from an end portion of said outer conductor and jacket, innerand outer quick coupling-decoupling cable terminal elements respectivelyelectrically connected to said end portions of said inner and outerconductors, said outer terminal element spaced longitudinally rearwardfrom said inner terminal element, an insulating body projecting from aconductive panel of electrical equipment, said body having an elongatedbore normal to the panel and in coextensive registration with anaperture therethrough, a quick coupling-decoupling equipment innerterminal element disposed at the end of said bore in spaced relation tosaid panel and adapted for connection to electrical circuitry of saidequipment, a quick coupling-decoupling equipment outer terminal elementelectrically connected to Said panel and disposed about said aperture,said inner and outer equipment terminal elements respectivelycomplementary to said inner and outer cable terminal elements andreleasably engaged thereby with said extended sleeve portion coaxiallydisposed within said bore and deiining With the Wall thereof an annularair space separating the engaged inner and outer terminal elements, andhermetic seal means disposed within said space to compartmentalize sameinto a longitudinal succession of sealed chambers while permitting asliding t between said extended sleeve portion and the Wall of saidbore.

2. A coaxial connector according to claim 1, further dened by saidhermetic seal means comprising a plurality of coaxially spaced resilientO-rings partially recessed into circumferential grooves formed in theWall projecting coaxially from the end of said inner conductor andextended sleeve portion, said equipment inner terminal element being ajack coaxially disposed at the end of said bore and releasably engagedby said plug, said cable outer terminal element being a cap coaxiallydisposed upon said extended sleeve portion, and said equipment outerterminal element being an annular boss projecting from said panel incircumscribing relation to said aperture and releasably engaged by saidcap.

4. A coaxial connector according to claim 3, further defined by saidhermetic seal means comprising a plurality of coaxially spaced resilientO-.rings partially recessed into circumferential grooves formed in thewall of said bore and compressively engaging the perpihery of saidextended sleeve portion.

5. A coaxial connector according to claim 4, further defined by saidextended sleeve portion having a tapered end terminating at said plug.

References Cited UNITED STATES PATENTS 2,296,766 9/ 1942 Bruno 174-222,442,545 6/1948 Koch et al. 174-152 2,496,938 2/ 1950 Friedman 174-842,625,579 1/1953 Frazee 174-77 3,319,211 5/1967 Smith et al 339-31STEPHEN J. NOVOSAD, Primary Examiner of said bore and compressivelyengaging the periphery 80 L. I. STAAB, Assistant Examiner of saidextended sleeve portion.

3. A coaxial connector according to claim 1, further defined by saidcable inner terminal element being a plug

